Process for preserving fresh whole milk



Patented June 26, 1934 UNITED STATES PATENT OFFICE Byron H. Webb,Washington, D. C.

No Drawing. Application April 30, 1934, Serial No. 723,183

2 Claims. (01. 99-8) (Granted under the act of March 3, 1883, as

7 amended April 30, 1928; 370 O. G. 757) This application is in part acontinuation of my application bearing Serial No. 607,517, filed April25, 1932, in the United States Patent Oflice.

This application is made under the act of March 3, 1883, as amended bythe act of April 30, 1928, and the invention herein described andclaimed may be used by or for the Government of the United States or anyof its officers or employees in the prosecution of work for the Govwernment or by any citizen of the United States.

without payment to me of any royalty thereon.

The high cost of market milk in large cities at the present time is apartial result of the expense of bottling and delivering the product inthe city 115 plant and of the necessity of limiting the milk shed of anygiven city to its immediate vicinity where the time required fortransportation is not excessive.

Fresh milk is often not available at any price,

as for example on board ships at sea, or in isolated communities wherecows are not kept. In such places it is necessary to rely uponartificial means of preservation. Sweetened condensed, evaporated andpowdered milks, which are the prod- 95 ucts generally used under suchconditions, all lack the natural fine flavor of fresh milk.

The value of a method of treating milk which might eliminate the citybottling of the product, reduce much of the bulk of milk by removal ofits water and make it possible to store milk or to ship it much longerdistances than is done at present, still maintaining its freshness andfine flavor, will thus become obvious.

If plain fresh milk is frozen and later thawed,

5 it will be found that the original structure of the melted milk hasbeen destroyed. The butter fat emulsion is destroyed and the fat risesto the surface unprotected by the milk colloids which originally kept itin the emulsoid state.

The discovery which I have made is that if the concentration of milkprotein is increased to a suflicient extent, this protein material willprotect the fat emulsion during freezing. When the frozen milk issubsequently thawed the fat emulsion remains intact and a smooth fineconsistency of body in the product is maintained. I have found itnecessary to concentrate the milk to onethird of its original weight inorder to secure a high enough milk-solids-not-fat concentration toprotect the fat emulsion during severe freezing conditions (i. e. slowfreezing). I have also observed that if a milk is frozen at aconcentration greater than 3 to 1, for example 4 to 1, a rapidthickening during storage in the frozen state oc- 55 curs, resulting inthe formation of a more or less water insoluble gel after two or threeweeks storage. When a milk concentration of 3 to 1 is used this gelformation does not set in before 7 to 10 weeks, depending upon thestorage temperatures used, the colder temperatures inhibiting gelformation.

Milk which is condensed 3 to 1 and held frozen for periods up to eightweeks may be easily reconstituted by the addition of the required amountof hot or cold water. By this process fresh milk 85 can be pasteurized,concentrated to one-third of its original weight, cooled, packaged, andfrozen at a point distant from the ultimate consumer .and retaileddirectly without further handling or contamination of the product.

An example of the process covered bymy invention is as follows: 100pounds of fresh milk is pasteurized at 145 F., for 30 minutes andcondensed in a vacuum pan by removal of 6'7 pounds of water. The 33pounds of concentrated milk is then cooled to 50 F. and immediately runinto 14 oz. tin cans. The cans are sealed and frozen in air at 10 F. Themilk is stored at 10 F., or lower until a short time before it is to beused. It is reconstituted by the addition of two times its volume ofwarm water. The flavor of the milk and the appearance of the cream layerupon standing are entirely similar to that of normal milk.

Having thus fully described my invention, what I claim is:

1. The process of preserving fresh whole milk without producingpermanent changes in its physical equilibria, which comprisespasteurizing the milk, condensing it under vacuum thereby removing atleast two-thirds of the water present, thence reducing the temperatureof the condensed milk to not more than 50 F., and thereafter packagingand freezing the product.

2. The process of preserving fresh whole milk without producingpermanent changes in its physical equilibria, which comprisespasteurizing the milk, condensing it under vacuum thereby removing atleast two-thirds of the water present. thence reducing the temperatureof the condensed 100 milk to not more than 50 F., and thereafterpackaging and freezing the product, and storing the frozen product at atemperature of substantially 10 F., and so retaining the said product atsuch a temperature until ready for consumption. 105

BYRON H. WEBB.

